U.S. patent number 7,408,732 [Application Number 11/288,651] was granted by the patent office on 2008-08-05 for shock resistant, high reliability rotating magnetic storage device and method.
This patent grant is currently assigned to Hitachi Global Storage Technologies Netherlands B.V.. Invention is credited to Masashi Kisaka, Yutaka Ozawa, Kenji Toga.
United States Patent |
7,408,732 |
Kisaka , et al. |
August 5, 2008 |
**Please see images for:
( Certificate of Correction ) ** |
Shock resistant, high reliability rotating magnetic storage device
and method
Abstract
An information recording method in a rotating storage apparatus
comprising a rotating recording medium for recording information, a
head for performing at least a write operation onto the rotating
recording medium, and an acceleration sensor for detecting a shock.
The method comprises outputting a shock out signal if an output
from the acceleration sensor exceeds a predetermined threshold. A
signal is output at a first level for a write inhibit period in
response to the input of the shock out signal, where the write
inhibit period is selected based at least in part on a time span in
which the output of the acceleration sensor exceeds the
predetermined threshold. Writing to the rotating recording medium
is prohibited during the write inhibit period.
Inventors: |
Kisaka; Masashi (Yokohama,
JP), Ozawa; Yutaka (Fujisawa, JP), Toga;
Kenji (Fujisawa, JP) |
Assignee: |
Hitachi Global Storage Technologies
Netherlands B.V. (Amsterdam, NL)
|
Family
ID: |
18605555 |
Appl.
No.: |
11/288,651 |
Filed: |
November 29, 2005 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20060077587 A1 |
Apr 13, 2006 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
10793318 |
Mar 3, 2004 |
7002766 |
|
|
|
09813081 |
Mar 19, 2001 |
6754021 |
|
|
|
Foreign Application Priority Data
|
|
|
|
|
Mar 28, 2000 [JP] |
|
|
2000-089857 |
|
Current U.S.
Class: |
360/60; 360/69;
360/75; G9B/19.005; G9B/5.198 |
Current CPC
Class: |
G11B
5/5582 (20130101); G11B 19/04 (20130101); G11B
33/08 (20130101); G11B 25/043 (20130101); G11B
21/12 (20130101) |
Current International
Class: |
G11B
19/04 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
5491394 |
February 1996 |
Harwood et al. |
6115200 |
September 2000 |
Allen et al. |
6429990 |
August 2002 |
Serrano et al. |
6754021 |
June 2004 |
Kisaka et al. |
6882489 |
April 2005 |
Brunnett et al. |
7002766 |
February 2006 |
Kisaka et al. |
|
Foreign Patent Documents
|
|
|
|
|
|
|
11126412 |
|
May 1999 |
|
JP |
|
WO 94/11874 |
|
May 1994 |
|
WO |
|
Primary Examiner: Wellington; Andrea
Assistant Examiner: Davidson; Dan I
Attorney, Agent or Firm: Zilka-Kotab, PC
Parent Case Text
RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser.
No. 10/793,318 to Kisaka et al., filed Mar. 3, 2004, now U.S. Pat.
No. 7,002,766 which is a continuation of U.S. patent application
Ser. No. 09/813,081 to Kisaka et al., filed Mar. 19, 2001 and now
U.S. Pat. No. 6,754,021.
Claims
We claim:
1. An information recording method in a storage apparatus
comprising a rotating recording medium for recording information, a
head for performing at least a write operation onto the rotating
recording medium, and an acceleration sensor for detecting a shock,
the method comprising; outputting a shock out signal if an output
from the acceleration sensor exceeds a predetermined threshold;
outputting a signal for a write inhibit period in response to the
input of the shock out signal, wherein the write inhibit period is
selected based at least in part on a time span in which the output
of the acceleration sensor exceeds the predetermined threshold; and
prohibiting writing to the rotating recording medium while the
signal is being output during the write inhibit period.
2. A method as recited in claim 1, wherein the write inhibit period
is further based at least in part based on an output peak value of
the acceleration sensor.
3. A method as recited in claim 1, further comprising generating a
logical AND signal of a logical negation signal of the signal at a
first level and a write gate signal output, the write gate signal
output being at the first level when a write permission is given;
and enabling a write onto the rotating recording medium when the
logical AND signal is at the first level.
4. A method as recited in claim 1, wherein the write inhibit period
is longer than a period that the output fron the acceleration
sensor exceeds the predetermined threshold.
5. A method as recited in claim 1, wherein the write inhibit period
is selected by varying a predetermined fixed time period based at
least in part on the time span in which the acceleration sensor
output exceeds the threshold.
6. A method as recited in claim 1, wherein the write inhibit period
is further selected by varying a predetermined fixed time period
based at least in part on the peak value of the acceleration sensor
output.
7. A method as recited in claim 1, wherein the acceleration sensor
is selected from a group consisting of a gravitational acceleration
sensor, a gyro-meter, and a semiconductor sensor.
8. A method as recited in claim 1, wherein the storage apparatus is
a hard disk drive.
9. A method as recited in claim 1, wherein the storage apparatus is
removable from a host system.
10. A method as recited in claim 1, wherein the rotating recording
medium is an optical disk.
11. An information recording method in a data storage apparatus
comprising; performing at a write operation onto a recording
medium; receiving output from an acceleration sensor the
acceleration sensor output indicating that a shock has been
detected; outputting a write gate signal at a first level when a
write permission is given; outputting a latch signal at the first
level for a write inhibit period upon detecting the output from the
acceleration sensor regardless of whether the write gate is at the
first level or at a second level, wherein the write inhibit period
is selected based on the acceleration sensor output; and enabling a
write onto the recording medium when the latch signal is at a
second level other than the first level and when the write gate
signal is at the first level.
12. A method as recited in claim 11, wherein the write inhibit
period is selected based at least in part on a time span in which
the acceleration sensor output exceeds a predetermined
threshold.
13. A method as recited in claim 11, wherein the write inhibit
period is selected based at least in part on a peak value of the
acceleration sensor output.
14. A method as recited in claim 11, wherein the write inhibit
period is further selected based at least in part on a waveform of
the acceleration sensor output.
15. A method as recited in claim 11, wherein the write inhibit
period is longer than a period that the output from the
acceleration sensor exceeds the predetermined threshold.
16. A method as recited in claim 11, wherein the write inhibit
period is selected by varying a predetermined fixed time period
based at least in part on the time span in which the acceleration
sensor output exceeds the threshold.
17. A method as recited in claim 11, wherein the write inhibit
period is further selected by varying, a predetermined fixed time
period based at least in part on the peak value of the acceleration
sensor output.
18. A method as recited in claim 11, wherein the acceleration
sensor is selected from a group consisting of a gravitational
acceleration sensor, a gyro-meter, and a semiconductor sensor.
19. A method as recited in claim 11, wherein the storage apparatus
is a hard disk drive.
20. A method as recited in claim 11, wherein the storage apparatus
is removable from a host system.
21. A method as recited in claim 11, wherein the recording medium
is an optical disk.
22. An information recording method in a storage apparatus
comprising a head for performing at least a write operation onto a
recording medium and an acceleration sensor for detecting a shock,
the method comprising; receiving an output from the acceleradon
sensor; determining whether the acceleration sensor output exceeds
a predetermined threshold; if the acceleration sensor output
exceeds the predetermined threshold, determining a time span in
which the output of the acceleration sensor exceeds the
predetermined threshold; selecting a write inhibit period based at
least in part on the time span in which the output of the
acceleration sensor exceeds the predeterimned threshold; and
prohibittng writing to the recording medium during the write
inhibit period.
Description
BACKGROUND OF THE INVENTION
1.Field of the Invention
The present invention relates to a rotating storage apparatus and
information recording method, and in particular, to protective
measures against shock and vibration during the operation of
information storage apparatus in which information is recorded on a
rotating recording medium such as a hard disk.
2.Description of the Background Art
In recent years, information processing systems have been widely
used in portable devices such as notebook personal computers. In
portable devices, vibration and shock are unavoidable and
protective measures against vibration and shock have become
important. Improvement of shock resistance is a very important
especially in a storage apparatus containing a rotating recording
medium such as a hard disk because it has a moving mechanism for
changing relative positional relationship between a head having
read/write capability and the rotating medium.
As is known to those skilled in the art, tracks are provided on a
rotating recording medium (hard disk) in hard disk drive, for
example, and a head is positioned over a track to record a magnetic
signal from the head in the track. If the head underwent external
shock or vibration while the head is positioned over a track and
information from the head is being recorded (written) in the track,
the head would go off the predetermined track (off-tracking) and
the information would be written in a position at a distance from
the predetermined track. The information written in such an
off-tracking condition may not only cause a read error but also, if
information has been recorded in adjacent tracks, affect the
adjacent tracks to prevent the information from being recorded
correctly.
Examples of approaches for preventing information recording in an
off-tracking condition includes a technology described in Published
Unexamined Patent Application No. 1-126412(Japan). The technology
is described in that application which has the object of improving
the performance of a rotating recording apparatus in an environment
in which the apparatus undergoes a shock. In particular, the timing
control is optimized for a retry operation according to the
affecting magnitude of shock force or vibration. An optimum retry
interval is set according to the magnitude of the shock or
vibration from retry intervals stored in memory to cause a data
write operation to be retried with an optimum timing if the shock
or vibration is detected to halt the write operation. In this way,
the number of retries or wasteful latency could be reduced compared
with the case where a fixed retry latency is determined, thereby
improving the performance of the apparatus.
However, the technology described in that application and other
prior-art technologies have the following problems. A gravitational
acceleration sensor (G-sensor) is used to detect a shock and
vibration. The physical quantity detected by the G-sensor is
acceleration (proportional to force) and does not exactly reflect
the off-tracking amount described above. The off-tracking amount is
a displacement (position) from an intended track position at which
a head is to be positioned. Although a shock or vibration (force)
causes the displacement of the head and therefore off-tracking, an
output from the G-sensor does not directory represent the
off-tracking amount. Because a position is typically represented by
the double integral of force in a system in which a feedback is
provided, such as the head positioning control system of a hard
disc drive, an actual off-tracking amount is provided with time
delay with respect to the output of the sensor. As a result, a
problem arises if a pulse-like shock that is as short as the time
delay is exerted, as described below. This problem will be
described with reference to FIG. 6.
FIG. 6A shows a logic circuit diagram for explaining the problem.
FIG. 6B shows a diagrammatic drawing. As shown in FIG. 6A, a shock
output signal 101 (called a shock out), which is present if an
output from the G-sensor exceeds a predetermined threshold, is
referenced when a write gate signal 102 is asserted (goes high).
When both of the shock out signal 101 and the write gate signal 102
are high, the output of an AND circuit 103 goes high and is latched
by a latch circuit 104 for a predetermined time period and a write
inhibit signal is generated. The write inhibit signal is inverted
by a NOT circuit 105 and input to an AND circuit 106 to mask the
write gate signal 102 (force it low). This inhibits the write
operation. In other words, the shock out signal 101 is referenced
only when the write gate is open and the write inhibit signal is
not generated when the write gate is closed (the write gate signal
102 is low).
This will be described in time sequence with reference to FIG. 6B.
Curve 110 is a waveform representing, with respect to the
time-axis, an output from the G-sensor when a short pulse shock is
exerted. The shock out signal 101 is continuously output in the
output waveform of curve 110 while a threshold 111 is exceeded.
However, unless the write gate signal 102 is asserted (high), no
write inhibit signal is generated, as described above. Here, no
problem would occur if the phase of the waveform 110 of the sensor
output matches that of off-tracking amount at the position of the
head. However, an actual off-tracking at the head position is
delayed with respect to the sensor output waveform of curve 110 as
shown by curve 113. If the write gate signal 102 is asserted (high)
at time t2 immediately after the time (t1) at which the shock out
signal 101 stops, no write inhibit signal would be generated and a
write operation start because the shock out signal 101 is not high
even though the head position is off-track.
The inventors of the present invention have found that the
above-mentioned problem was likely to arise when a hard disk drive
is installed in a portable computer, which in turn is particularly
susceptible to an external shock and vibration. Also the problem is
more pronounced as the recording density increases. For example,
the above-mentioned problem is likely to occur when the storage
density is increased to about 30 ktpi or over in a typical hard
disk drive of 4,200 rpm.
What is needed is a disk drive with more robust resistance to shock
disturbances.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus
and method of achieving high recording reliability of a rotating
storage apparatus which uses a high-density storage medium, even in
an environment where a shock or vibration exists. It is another
object of the present invention to provide an apparatus and method
that can inhibit a write operation in an off-tracking condition
even in an environment where a short pulse shock or high-frequency
vibration is exerted. It is yet another object of the present
invention to provide an apparatus and method for an optimum write
inhibit according to the magnitude of a shock or the amplitude of
vibration and that can increase the writing speed as well as the
reliability of the apparatus to improve the performance of the
apparatus.
The outline of the present invention will be described below. The
rotating storage apparatus of the present invention comprises a
rotating recording medium for recording information, a head for
performing at least a write operation onto the rotating recording
medium, and an acceleration sensor for detecting a shock. If an
output from the acceleration sensor exceeds a predetermined
threshold, the write operation is inhibited during a predetermined
write inhibit period regardless of the status of a write gate
signal.
The rotating storage apparatus of the present invention comprises a
rotating recording medium for recording information, a head for
performing at least a write operation onto the rotating recording
medium, and an acceleration sensor for detecting a shock. The
apparatus comprises 1) means for monitoring an output from the
accelertion sensor and, if the monitored output exceeds a
predetermined threshold, outputting a shock out signal 2) latch
means for outputting a latch signal at a first level during a
predetermined write inhibit period from a time at which the shock
out signal is input 3) write gate signal generation means for
outputting the signal at the first level when a write permission is
given and 4) a logic enabling a write onto the rotating recording
medium when the latch signal is at a second level other than the
first level and when the write gate signal is at the first
level.
The information recording method of the present invention is a
method for recording information in a rotating storage apparatus
comprising a rotating recording medium for recording information, a
head for performing at least a write operation onto the rotating
recording medium, and an acceleration sensor for detecting a shock.
The method comprises 1) outputting a shock out signal if an output
from the acceleration sensor exceeds a predetermined threshold 2)
outputting continuously a signal at a first level for a
predetermined write inhibit period in response to the input of the
shock out signal 3) generating a logical AND signal of a logical
negation signal at a first level and a write gate signal output,
the write gate signal becomes the first level when a write
permission is given and 4) enabling a write onto the rotating
recording medium when the logical AND signal is at the first
level.
According to the above-described rotating storage apparatus or
information recording method, a write inhibit signal is generated
at the time when a shock out signal is detected, regardless of the
status of the write gate. The write inhibit signal is referenced
and if the apparatus is in the write inhibit state, a write gate
signal is masked (negated, goes low). The period (write inhibit
period) during which the write inhibit signal is continuously
output after the shock out signal is detected is predetermined by
taking the characteristics of the apparatus into account, and in
addition, changed by referencing the width of the output signal or
the peak value of the acceleration sensor. This ensures that the
write inhibit signal is generated to inhibit a write operation in
an off-tracking condition whenever the head is in the off-tracking
condition in an environment in which a short pulse-like shock or
high-frequency vibration is exerted on the apparatus. Thus, the
information recording reliability of the apparatus can be
increased. In addition, the write time can be reduced by selecting
an optimum write inhibit duration, thereby improving the
performance of the apparatus.
High recording reliability of a rotating storage medium apparatus
using a high-density recording medium can be achieved even in an
environment where a shock or vibration exists.
A write operation in an off-tracking condition can be inhibited
even in an environment where a short pulse shock or high-frequency
vibration may be exerted.
An optimum write inhibit operation can be performed according to
the magnitude of a shock or the amplitude of vibration, thus
improving the writing speed and performance as well as the
reliability of the apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an example of a hard disk drive of
an embodiment of the present invention.
FIG. 2 is a block diagram showing an example of the hard disk drive
of the embodiment of the present invention.
FIG. 3 is a circuit block diagram showing part of a hard disk
controller.
FIG. 4 is a chart showing the timing of outputs from major parts of
the circuit, the waveform of outputs of an acceleration sensor, an
off-tracking amount.
FIG. 5 is a block diagram showing a circuit for determining a
change of write inhibit period.
FIG. 6A is a logic circuit diagram of the prior art.
FIG. 6B is a chart for explaining the prior art.
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with
reference to the accompanying drawings. However, the present
invention may be implemented in many different embodiments and
should not be construed as being limited to the description of the
embodiment. Throughout the description of the embodiment, like
elements are labeled with like numbers.
FIG. 1 is a perspective view showing an example of a hard disk
drive, which is one embodiment of the present invention. FIG. 2 is
a block diagram of the hard disk drive. The hard disk drive of this
embodiment comprises a disc-like magnetic recording medium 1 on
which information is magnetically recorded, a spindle motor 2 for
driving the magnetic recording medium 1, a magnetic head 3 for
recording information on the magnetic recording medium 1 or reading
from information recorded on the magnetic recording medium 1, an
arm 4 for supporting the magnetic head 3, a voice coil motor 5 for
driving the arm 4, and a hard disk controller 6 for controlling
input and output of information into and from the magnetic head 3
and the drive of the spindle motor 2 and voice coil motor 5. Data
writing and reading to and from the magnetic head 3 are performed
through a flexible cable 8 attached to a connector 7 and the arm 4.
A gravitational acceleration sensor 9 is attached to the flexible
cable 8. While the gravitational acceleration sensor 9 is shown as
attached to a movable part of the flexible cable 8 in FIG. 1 for
clarity, it is in practice attached to a cable connection part in
the close proximity of the connector 7 so that vibration of the
cable is not detected by the gravitational acceleration sensor
9.
The hard disk controller 6 interfaces to a host computer 10 and
reads or writes information from or onto the magnetic recording
medium 1 as magnetic information, according to a read or write
request from the host computer 10. FIG. 3 is a circuit block
diagram of part of the hard disk controller 6. FIG. 4 shows a chart
of the output timing from major parts of the circuit and the
waveform of outputs from the gravitational acceleration sensor and
the off-tracking amount of the head.
The circuit block shown in FIG. 3 consists of a latch circuit 21
for latching a shock out signal SO, a NOT circuit 22 for negating
the output from the latch circuit 21, and an AND circuit 23 to
which the output from the NOT circuit 22 and a write gate signal WG
are provided as its inputs.
FIG. 4A is a chart showing the waveform of an output from the
gravitational acceleration sensor 9 in response to a shock exerted
on the drive apparatus. It is assumed that waveform 30 as shown is
output when a short pulse shock is exerted. An output (shock out
signal SO) 33 as shown in FIG. 4B is continuously output from the
sensor during the time period in which the waveform 30 exceeds a
predetermined threshold 31. The displacement (off-tracking amount)
from a track position of the magnetic head 3 caused by this shock
is indicated by curve 34 in FIG. 4C The off-tracking amount (curve
34 is a physical quantity having a distance dimension and
represented by a double integral as mentioned earlier, and
therefore has time delay with respect to the sensor output
(waveform 30).
According to the present invention, a write inhibit signal 35 is
generated as shown in FIG. 4D in order to inhibit a write operation
while such off-tracking exists. The write inhibit signal 35 is
generated by the circuit block shown in FIG. 3. That is, the shock
out signal SO is generated by shock out generating means (not
shown) and input into the latch circuit 21. The output of the latch
circuit 21 is held high during a predetermined time period after
time t3 at which the shock out signal SO is detected (write inhibit
period (t4-t3). The output signal from the latch circuit 21 is
converted into low by the NOT circuit 22. In other words, during
the write inhibit period, a low-level signal is input into the AND
circuit 23 and the output from the AND signal 23 goes low
regardless of the status of the write gate signal WG to keep the
write inhibit state.
In this way, according to the present invention, a write operation
is inhibited during a predetermined period(write inhibit period)
after a shock out signal SO is detected, regardless of the status
of the write gate WG. Thus, the write inhibit state can be kept to
inhibit a write operation in an off-tracking condition even if a
short pulse shock is exerted.
As shown in FIG. 4E, the output 36 (final write gate output) from
the AND circuit 23 does not continuously go high (asserted) even if
the write gate (WG) is asserted (goes high) at time t5 during the
write inhibit period, and goes high (asserted) at time t6 by a
retry after the end of the write inhibit period. The asserted state
(high level) of the write gate signal 36 forces a write signal 37
onto the magnetic recording medium 1 to be output. Examples of the
write signal 37 includes a synchronous signal, address signal, user
data signal, and error correction code signal. The write inhibit
period (t4-t3), that is, a latch period by the latch circuit 21,
can be fixed in appropriate time periods by analyzing the variation
characteristics of the arm 4 and other components beforehand by
experiments and reflecting the results of the experiments in the
determination. It has been empirically found that a period
equivalent to 15 servo sectors is appropriate. Because the sampling
frequency for one servo sector is 5.6 kHz, about 2.7 msec may be
appropriate.
The write inhibit period may be varied in consideration of an
output value from the gravitational acceleration sensor 9. FIG. 5
is a block diagram showing an example of a circuit for determining
a change of write inhibit period. This circuit is contained in the
hard disk controller 6, for example.
An output signal (Sig) from the gravitational acceleration sensor 9
is input into an amplifier (AMP) 40. The output of the AMP 40 is
input into a window comparator 41 and an analog-digital converter
(ADC) 42. The window comparator 41 outputs the high-level signal
when a signal exceeding a predetermined threshold is input. The
time span in which the output is held high is measured by a pulse
width measurement circuit 43. The measured value is input into a
micro processing unit (MPU) 44, where a write inhibit period is
calculated according to the time span measured by the pulse width
measurement circuit 43. A controller MPU installed in a hard disk
controller 6 may also be used as the MPU 44.
On the other hand, a signal converted into a digital signal in the
ADC 42 is input into the MPU 44 and the largest value (the peak
value of the signal) is selected and a write inhibit period
according to the peak value is calculated in the MPU 44.
The write inhibit period calculated in the MPU 44 can be input into
the latch circuit 21 in FIG. 3 and the write inhibit period is set
as the latch period. In this way, the write inhibit period can be
varied according to the signal width or peak value of the
gravitational acceleration sensor 9, thereby allowing an optimum
write inhibit period to be set according to the output value of the
gravitational acceleration sensor 9 by a program provided to the
MPU 44. Of course, findings in experiments and studies can be
reflected in the optimization of this program.
Any methods that take into account only the pulse width value, only
the peak value, or both of the pulse width and peak value may be
used for the calculation of the write inhibit period by the MPU
44.
While the present invention by the inventors has been described in
particular with respect to the embodiment of the present invention,
the present invention is not limited to the above-described
embodiment. Various changes may be made to the present invention
without departing from the scope and spirit of the present
invention. For example, while the embodiment has been described
with respect to the hard disk drive as an example of the rotating
storage apparatus, the present invention is not limited to the hard
disk drive. Instead, the present invention may be applied to any
storage apparatus having a rotating recording medium, including a
rewritable optical and magneto-optical recording apparatus such as
CD-R/W, DVD, and MO drive storage apparatuses. In addition, the
present invention may be applied to a removable rotating magnetic
recording apparatus.
Any acceleration sensors, including a dielectric sensor such as a
gyro-meter, and a semiconductor sensor may be used as the
acceleration sensor 9. In addition, while the example in which the
time span and peak value of the sensor output are referenced to
vary the write inhibit period has been described, the sensor output
waveform may be analyzed by using an appropriate method such as
fast-Fourier-transform processing and the result of the analysis
may be used to calculate the write inhibit period more
precisely.
* * * * *